The T-VSSI researchers installed an Infiltration Gallery at the Pennypack Ecological Restoration Trust (PERT), located within the Pennypack Creek Watershed. The selected location at PERT for the infiltration gallery is at the low point of the PERT parking lot where it will receive the largest stormwater flows. Approximately 4.5 acres drain to the infiltration gallery. Of those 4.5 acres, approximately 30% are impervious and the remainder is either forest or mowed grass lawn.
In August 2006, the T-VSSI project team constructed a small Infiltration Gallery beneath a portion of the parking lot at the Pennypack Ecological Restoration Trust’s (PERT’s) main entrance. The infiltration gallery is a retrofit to an existing parking lot, designed to capture, retain, and infiltrate the “2-year, 24-hour” storm event, which equates to approximately 3.3 inches of precipitation. The retrofit is also designed to pre-treat stormwater to remove sediment, floatables, and grit. The gallery will receive runoff from the 4.5-acre upgradient drainage area and thereby reduce non-point source runoff within the upper Pennypack Creek watershed.
The infiltration gallery consists of an underground earthen-walled chamber, approximately 25 x 39 feet, which houses five (5) 32.5 feet long Recharger 330s, a modular prefabricated stormwater management system by CULTEC Inc. The Recharger 330s rest on a bed of and are covered by crushed stone. Washed to remove fines, the crushed stone is encased in filter fabric and covered by compacted fill, pavement sub-base, which is covered with porous pavement. The chambers of the Recharger 330s and voids between the crushed stone provide stormwater storage.
Stormwater enters the infiltration gallery by two routes: one route is by flowing into a drop inlet and the other is through the porous paving covering the lower half of the infiltration gallery. The drop inlet has a sumped inlet (i.e., the outlet is above the bottom) and there is a Snout® that covers the outlet that connects to a Cultec, Inc. Stormfilter®, which filters the stormwater before it enters the infiltration gallery. The sumped inlet captures heavy particles carried in by stormwater, and the Snout® prevents floatables from entering the gallery. The Stormfilter® is the final site for particulate removal before the stormwater enters the infiltration gallery. Stormwater that is not captured in the drop inlet will be intercepted by the porous paving.
This is the first such installation in Southeastern Pennsylvania. The results of monitoring the gallery’s performance during wet-weather events could demonstrate the value of this type of BMP for retrofitting parking areas and for designing stormwater retention and infiltration facilities for new development instead of the more conventional surface storage facilities that consume valuable land.
The design goals of the infiltration gallery facility are to:
- Capture non-point source stormwater runoff from the parking lot area,
- Retain stormwater,
- Infiltrate stormwater, and
- Pre-treat stormwater to remove sediment, floatables, and grit.